Most likely, yes. Polyfuses have a hold current rating, which is the current that they can run at more or less indefinitely without tripping. As the current exceeds that threshold, it will start to heat. The material the fuse is made of is temperature sensitive and increases resistance as it heats. If it runs at current that exceeds it's hold rating long enough, eventually enough heat will be generated to cause the fuse to trip. The more it exceeds, the faster it will trip. As your heated bed cycles on and off, 12.55 amps probably is pushing it, but you'll just have to see. Hopefully your bed has an LED so you should be able to tell if the fuse trips when the LED on your electronics indicates that the bed should be on, but the bed's LED is off.Quote
My PSU puts out 12.55V. With 1.1ohm resistance the bed will draw 11.4A when cold which is just over the 11A polyfuse fuse capacity. With 1ohm resistance the bed will draw 12.55A when cold which is over the polyfuse capacity. Would this be too much? I understand the bed will draw fewer amps when it gets warm but can the fuse handle this surge when it's cold?
My bed has a .8 ohms resistance and I've yet to see my RAMPS polyfuse trip, and that would be with pulling 15 amps.